1. Field of the Invention
This invention relates to an ink jet recording apparatus provided with an ink jet head for effecting recording with flying ink droplets utilizing the film boiling phenomenon of liquid ink.
2. Related Background Art
In recent years, various ink jet recording methods have been put into practical use because in such recording methods, the creation of noise during recording is negligibly small and in addition, recording can be effected on plain paper.
Among such methods, the ink jet recording method described, for example, in Japanese Laid-Open Patent Application No. 54-59336 (the so-called bubble jet recording method) is such that heat energy is caused to act on ink and the ink subjected to the action of this heat energy undergoes a sudden volume change (film boiling phenomenon) resulting from a state change; by this action force, the ink is discharged from a discharge port at the end of a recording head unit, whereby flying ink droplets are formed and adhere to a recording medium to thereby accomplish recording.
The principle of ink droplet formation in such a recording method is that when an electro-thermal converting member is electrically energized, the ink in the heat-acting portion subjected to the action of the heat energy which is ink droplet forming energy undergoes a state change resulting from a sudden increase in volume; that is, the ink in the heat-acting portion causes the creation, growth and contraction of a bubble very momentarily, whereby liquid present between the heat-acting portion and the discharge opening is discharged as an ink droplet.
By repeating such a cycle of creation, growth, contracting and disappearance of the bubble, the ink is subjected to high heat. Therefore, thermally unstable ink is liable to undergo a chemical change and in the heat-acting portion, production and precipitation of insoluble matter may occur and eventually the recording head may become incapable of discharging the ink. Accordingly, to effect recording at a high speed for a long time by the use of such an apparatus, it is very important to improve the stability of the ink and on the other hand, to set the optimum driving conditions corresponding to the ink in the recording head.
FIG. 1 of the accompanying drawings shows variations with time in the surface temperature T of the heat-acting surface when an electrical signal of pulse waveform shown by P is input to a recording head having an electro-thermal converting member and the volume V of a bubble then created. When the pulse-like electrical signal P which is switched on and off is input to the electro-thermal converting member between a time t.sub.0 and a time t.sub.f, the surface temperature T of the heat-acting surface reaches a maximum temperature T.sub.P at the time t.sub.f.
Here, when T.sub.P is higher than the boiling point of the ink which is in contact with the heat-acting surface, a bubble begins to be created from a time t.sub.B0 at which T=T.sub.B in the heat-acting portion filled with the ink, and the volume thereof increases with the lapse of time and reaches a maximum volume V.sub.P at a time t.sub.p. When the electrical signal P is switched off at the time t.sub.f, the surface temperature T begins to attenuate gradually and accordingly, the volume V of the bubble decreases and the bubble disappears at a time t.sub.B1.
In order to ensure that the discharge of ink droplets is effected efficiently and stably in an ink jet recording apparatus, for example, in the bubble jet recording method described above, driving conditions for film boiling such as a voltage, a pulse width and a frequency at which electrical energy is supplied to the electro-thermal converting member, and further, control such as a pre-discharging or pre-heating for effecting stable practical printing, or the recovery operation of the recording head, are programmed in advance in the ink jet recording apparatus. Particularly, in a recording apparatus of the type in which an ink tank storing therein ink to be supplied to a recording head is interchangeable for the apparatus, if use is made of an ink cartridge storing therein ink of another kind which does not match these various set conditions, there will not be obtained an appropriate combination of the characteristics of the ink and the driving conditions and therefore, normal driving of the recording head cannot be accomplished and recording of high quality will become difficult. For this reason, usually, the form of the ink cartridge interchangeable for the recording apparatus is designed exclusively for each apparatus so that the user may not misuse the ink cartridge.
An example of the form of such an ink cartridge is a box-like form. The ink cartridge is designed so that by the operation of mounting the ink cartridge on a cartridge mounting portion, a hollow needle provided on the mounting portion is thrust in the rubber plug of the cartridge so that the ink may be supplied from an ink containing portion in the cartridge to an ink supply system through the hollow needle.
However, the conventional ink jet recording apparatus having such an interchangeable ink cartridge only permits the use of ink fit for the discharge conditions set in that apparatus, and cannot select ink of different discharge conditions; the range of use of the ink jet recording apparatus is therefore limited and a wide range of use of ink jet recording apparatus having an excellent recording characteristic has been difficult. Also, even if ink having more excellent discharge and recording characteristics is developed in the future, it will become impossible to use such ink or obtain satisfactory printing with the apparatus, because the program in the apparatus is not proper.
The above-noted problems will hereinafter be discussed specifically and in detail. Some examples of typical ink compositions usable in an ink jet recording apparatus are shown in Table 1 below.
TABLE 1 Kinds of ink/ component #1 #2 #3 Water [%] 50 50 80 DEG [%] 47 37 17 PEG [%] 0 10 0 Dyestuff [%] 3 3 3
Ink #1 is an example of standard ink which exhibits a popular performance in both viscosity and solidification. On the other hand, ink #2 is ink in which the percentage of the component difficult to volatilize is increased relative to the ink #1; relative to ink #2, ink #1 is characterized by a difficulty in clogging the discharge ports of the recording head. Thus, an ink jet recording apparatus using the ink #2 does not require a mechanism for preventing the clogging of the discharge ports during the downtime of the ink jet recording head, so that it can be structurally simplified. However, since the ink #2 has relatively high viscosity, it is necessary that discharge of the ink which does not contribute the recording, i.e., an operation called preliminary discharge, be sufficiently performed in advance in the early stage of each use. This may sometimes lead to a reduced throughput. Also, the ink #2 suffers from a disadvantage in that the ink readily blurs on the recording medium so that a very high quality of printing cannot be provided. Ink #3 is ink characterized in that the percentage of water content is increased relative to the ink #1 and the desiccation of the ink on the recording medium is quick, so that recording of high quality suffering much less from blurring can be accomplished. Further, the ink #3 has a feature in that it can be driven at a relatively high frequency because it permits quick refilling of the nozzle after discharge. However, the ink #3 is readily desiccated and therefore, the ink in the discharge ports of the recording is readily solidified during the downtime of the recording head. Therefore, it is necessary that the recovery operation, such as pumping and capping operations, be performed frequently during the downtime of the recording head. Particularly, where the ink #3 is used for a recording head of the bubble jet type in which heat energy is utilized as ink discharging energy, stable ink discharge cannot be accomplished unless the electrical energization time is made relatively short (e.g. 2-5 .mu.sec) and the driving voltage is made correspondingly high. Accordingly, in the case of a recording head which can withstand such high driving stress, printing of high quality can be accomplished, but otherwise there will be obtained printing of low quality because it suffers from a lack of accuracy in the location where the liquid droplet lands on the recording medium.
Table 2 below specifically shows some examples of the driving conditions for the recording head relative to the inks in Table 1.
TABLE 2 Examples of appa- Kinds of ink/ ratus Driving conditions #1 #2 #3 I Voltage [V] 21 21 28 Pulse width [.mu.s] 7 7 3 Frequency [Khz] 4.5 4.0 6.0 Number of 50 128 50 preliminary discharges (times) II Voltage [V] 21 19 21 Pulse width [.mu.s] 7 8.5 7 Frequency [Khz] 2 2 3 Number of 50 128 50 preliminary discharges (times)
The apparatus example I is an apparatus using a single crystal of silicon as the base material of the recording head and carrying thereon a recording head capable of withstanding short pulse energization and high voltage driving and responding to a high frequency. The apparatus example II is an apparatus using glass as the base material of the recording head and carrying thereon a recording head which is low in durability with respect to short pulse energization, high voltage driving and high frequency, but is very inexpensive.
For example, when the apparatus example I programmed with the use of the ink #1 having the standard characteristics being taken into account is used in a manner in which the frequency of use is extremely low, it is desirable to use the ink #2 which does not cause clogging. However, it is necessary that the user change without fail the substance of the driving program of the recording head in which are set the conditions for the best discharge to be accomplished when the ink #1 is used to the substances matching the characteristics of the ink #2; for example, the conditions such as the number of preliminary discharges, the pre-heating state, the driving frequency and the pulse width.
To increase the printing speed in apparatus example I, the ink #3 can be used, but even in that case, as described previously, it is necessary that the user change without fail the driving conditions of the recording head in accordance with the characteristic of the ink #3.
However, it is cumbersome and prone to error for the user to change the driving conditions in accordance with the characteristics of the ink used, and damage is liable to occur to the recording apparatus due to the malfunctioning of the recording head. For example, where use is made of a recording head of the type of the apparatus example II, when the conditions for the use of the ink #1 are to be changed to the driving conditions for the use of the ink #3, the head driving voltage is changed from 21V to 28V and the pulse width is changed from 7 .mu.sec to 3 .mu.sec, whereby there is provided good discharge of the ink #3. However, as previously described, such driving conditions are not suitable because they give high stress to the recording head used in the apparatus example II and may therefore drastically shorten the life of the recording head. Accordingly, when the life of the recording head is taken into consideration, for example, the driving voltage must be changed to 21V and the pulse width must be changed to the order of 7 .mu.sec and moreover, the frequency must be changed from 6 Khz to 3 Khz.
As described above, it is adequate to use ink which takes into account the conditions and the purpose of use of the ink jet recording apparatus, but it is difficult for an ordinary user to minutely change the program in the ink jet recording apparatus body such as the driving conditions and the preliminary discharge conditions of the recording head, with the kind and driving characteristics of the recording head taken into account to cope with a change in the ink. Even if such a change is possible at all, a wrong setting may be effected so that abnormal printing occurs or excessive stress is given to the recording head; it thus will be difficult to ensure the reliability of the recording apparatus.
Now, when an ink cartridge interchangeable for the apparatus is mounted in the apparatus body, the ink cartridge generally is held by a suitable fastening means. Also, when the ink cartridge is mounted, the interior of the ink tank and the ink supply system on the apparatus body are communicated with each other.
However, if the relation between the holding position of the fastening means and the position in which the communication is effected is not appropriate, or especially if there is a play in the fastening means, the ink communication will not be secured in spite of the ink tank being held by the fastening means, and the ink supply system and the ink tank will become spaced from each other. If at this time, for example, the recovery operation is performed, air may be introduced into the ink supply system. If air is thus introduced into the ink supply system, not only will ink discharge fail to be properly effected, but also the recording head will be damaged.
On the other hand, when the ink cartridge is to be interchanged, the user may inadvertently insert his hand into the cartridge insertion port and have his fingertip injured or stained with ink. In order to prevent this, there has been provided a protective device as shown, for example, in FIG. 2 of the accompanying drawings. In FIG. 2, the reference numeral 130 designates an ink tube connected to a hollow needle 120 and supplying ink to the recording head, the reference numeral 2131 denotes a mounting bed for fixedly supporting the hollow needle 120, and the reference numeral 2132 designates an insertion path for directing the ink cartridge 104 to its mounted position.
The reference numeral 133 denotes a protective plate pivotable about a support shaft 134, the reference numeral 135 designates a torsion coil spring mounted around the support shaft 134 and biasing the protective plate 133 in the direction of arrow C, and the reference numerals 136 and 137 denote locking members for holding the protective plate 133 in an insertion path closing position as shown and restraining the movement thereof. That is, these locking members 136 and 137 are formed symmetrically with respect to each other, and respectively have wedge portions 136A and 137A and locking grooves 136B and 137B at opposed locations, and are both endowed with resiliency, whereby they can be flexed in the direction of arrow D. The reference numeral 140 designates a rubber plug provided in the front face of the ink cartridge 104, and the reference numerals 141 and 142 denote unlocking projecting members (hereinafter referred to as the unlocking members) provided on the sides of the ink cartridge 104.
In the protective device for the ink cartridge mounting portion which is so constructed, as long as the ink cartridge 104 is not mounted, the protective plate 133 is held in its shown position by the locking members 136 and 137, and even if a finger tip or the like is inserted into a cartridge guide or the like, it will strike against the protective plate 133 and will not reach the tip end of the hollow needle 120. Also, if as shown in FIG. 2, the ink cartridge 104 is inserted in the direction of arrow A along the insertion path 132, the unlocking members 141 and 142 will slidably contact with the wedge portions 136A and 137A of the locking members 136 and 137, respectively, and will push open these members in the direction of arrow D.
Consequently, the opposite end portions of the protective plate 133 are liberated from the locking grooves 136B and 137B of members 136 and 137 also, the front face of the ink cartridge 104 bears against the protective plate 133 and pushes it up in the direction of arrow B. Thereafter, the hollow needle 120 thrusts into the rubber plug 140 of the ink cartridge 104, whereby there can be brought about a mounted state in which the supply of ink to the recording head is possible. When the ink cartridge 104 is to be removed, the ink cartridge 104 is pulled out rearwardly from its mounted state, whereby the hollow needle 120 is pulled out from the rubber plug 140, and then the protective plate 133 is pivoted in the direction of arrow C by the spring force of the torsion coil spring 135 so that it returns to its vertical position and is sandwiched between the locking members 136 and 137 and restored to the state shown in FIG. 2.
However, in the conventional ink jet recording apparatus as described above, the locking members 136 and 137 are provided laterally symmetrically. Therefore, even when the user inserts the ink cartridge 104 with its vertical direction or its longitudinal direction mistaken, the locked state of the protective plate 133 will be released by the engagement between the unlocking members 141, 142 and the locking members 136, 137 and the ink cartridge 104 will then be directed to its mounted position. This has led to the undesirable possibility that the hollow needle 120 is damaged or the ink cartridge 104 itself is damaged and the supply of ink becomes impossible. Also, an attempt to provide a special device discretely to prevent such an accident would make the mounting device itself complicated in structure and result in increased cost.
Now, some ink cartridges are in a form which is provided with an ink containing portion and in addition, a waste ink containing portion for containing discharge ink, i.e., ink sucked during the recovery operation performed to prevent the clogging of the ink discharge ports of the recording head (hereinafter referred to as the waste ink). With such ink cartridges, it is possible to discard the waste ink contained in the waste ink containing portion, by and simultaneously with the interchange of the cartridge.
If, in an ink jet recording apparatus using such an interchangeable ink cartridge, the recording operation is performed with no ink cartridge mounted in the apparatus, recording will not be obtained because ink supply does not take place. Also, if the recovery operation is performed, waste ink discharged from the waste ink system side of the apparatus will not be contained in the ink cartridge but instead may be released into the apparatus to thereby contaminate the environment, or the released waste ink may contaminate electric circuits to thereby cause accidents, such as a fire. Accordingly, it is desirable to provide detecting means for informing the user of the mounting of an ink cartridge in the apparatus.
An example of such a detecting means is shown in FIGS. 3 and 4 of the accompanying drawings. As shown in FIG. 3,a cartridge detecting flag 131 is comprised of a rotatable flag shaft 131B supported on the upper portion of an insertion port 121, a flag plate 131C mounted on one end of the shaft, and a cam portion 131A for rotating the flag shaft 131B. A lever member 132 pivotally moved by the mounting of a cartridge 104 is provided inside the insertion port 121. Thus, when the ink cartridge 104 is inserted into the insertion port 121 and is securely mounted with a hollow needle 120 being inserted into a tank, not shown, in the cartridge 104, the projected portion 132A of the lever member 132 is pressed by the forward end of the cartridge 104, whereby the tip end portion 132B of the lever pivotally moves the flag plate 131C through the cam portion 131A and keeps it in a light intercepting position for a detecting sensor 124 as shown.
FIG. 4 shows the details of the detecting sensor 124 for detecting both of the home position and the cartridge. The detecting sensor 124 is of the transmission type and is provided with an optical path 4135 between a light emitting element 4133 and a light receiving element 4134, and is designed such that the optical path 4135 is shielded from light by a home position detecting flag 4130 such as, for example, the flag plate 131C of the ink cartridge detecting flag 131, etc. Accordingly, when the ink cartridge 104 is mounted, the detecting sensor 124 detects the flag plate 131C when a carriage 102 has been directed to a detecting position, whereby the mounting of the cartridge is confirmed.
However, in the conventional ink jet recording apparatus as described above, the home position sensor is used also as the cartridge detecting sensor and the number of detecting means is correspondingly decreased, but the information the user wants to recognize about the ink cartridge 104 is not only the mounting thereof, but also information regarding the color and characteristics of the ink contained in the ink cartridge 104 as described previously as well as the remaining amount of ink. To enable all of such information to be obtained, the number of flags must be increased or the number of detecting means themselves must be increased; this will result in more complicated structure, which in turn will result in an increased cost.